Locate the building that has 2 or 3 doors on level 4. Press A+Up to reach the window between the doors and access a bonus cave.
To get over sets of rocks with 3 layers, you must buy straw sandals. Buy at least 10 sandals. Go to the first level and jump under the bell. Therer will be a stone pillar there. Hit it with yoru sword and jump in. At the nend of the tunnel are three layer of rocks. Jump over them with your sandals and you will get a gold cat.
A Gradius Mini-Game can be played at one of the carnival booths.
Rapidly tap B during the lottery drawing.